a. Field of the Invention
This invention relates to a system and method for identifying physical structures in a body. In particular, the instant invention relates to a system and method that identify the location of physical structures based on fluid flow within the body as shown in images of the body.
b. Background Art
The flow of a fluid such as blood within a region of interest in a body can be detected and illustrated in images of the region. In particular, ultrasound transducers disposed within the cardiovascular system can detect a Doppler shift (or change in frequency and wavelength) in waves associated with the blood as it moves relative to the transducers. Using information from the transducers, an electronic control unit can generate image data used to illustrate the blood flow within the region. Within the image, the blood flow is often colored using predetermined colors depending on whether the blood is flowing towards or away from the transducers. Based on the illustrated flow of blood and its color, a clinician can often identify physical structures within the image. For example, with the transducer placed in the left atrium of the heart, blood flowing away from the transducer is indicative of blood flowing outward through the mitral valve and into the left ventricle. Similarly, blood flowing towards the transducer is indicative of blood flowing into the left atrium from the pulmonary veins. While existing technologies permit the clinician to estimate blood flow velocity and to confirm the identify of physical structures by viewing the direction, timing and speed of blood flow in the image, these technologies do not permit a precise identification of the location of a physical structure.
Blood flow is often detected and imaged through intracardiac echocardiography (ICE) using an ultrasound transducer disposed on a catheter threaded through the vasculature of the body. Some conventional systems can have attached optical or magnetic position and orientation sensors to the ICE catheter to enable registration of the image captured by the ICE catheter within the three dimensional coordinate system. The accuracy of registration is impacted by variations in the manufacture and implementation of the ICE catheter and the position and orientation sensors. In position and orientation sensing systems based on electric fields, there can also be instability and variations in the navigational potential field and the reference electrodes. Calibration of position and orientation sensors on the catheter is therefore necessary. Calibration of sensors based on electric fields is presently accomplished via registration to some other sensing technology, typically magnetic. Such registration requires manufacture of a catheter with both magnetic and electric field sensors. Consequently, there is utility in calibration of an electric-field sensor on an ICE catheter using information present in the ultrasound data.
The inventors herein have recognized a need for a system and method for identifying the location of physical structures in the body that will minimize and/or eliminate one or more of the above-identified deficiencies.